Inhaler

ABSTRACT

An inhaler for delivery of medicament from a canister which is compressible to deliver a dose of medicament. The inhaler comprises a housing ( 1 ) for holding a canister ( 2 ), the housing having a mouthpiece ( 5 ) for inhalation of a dose of medicament delivered by the canister ( 2 ) and a breath-actuated actuation mechanism ( 6 ) for compressing a canister ( 2 ) held in the housing ( 1 ) in response to inhalation at the mouthpiece ( 5 ). The actuation mechanism ( 6 ) includes a vane in the form of a flap ( 13 ) disposed across a duct ( 24, 32 ) extending from the mouth piece ( 5 ) arranged to lock the canister ( 2 ) in a compressed state and being responsive to the inhalation at the mouthpiece ( 5 ) to release the canister ( 2 ) when the level of inhalation at the mouthpiece falls below a predetermined threshold.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a national phase application under 35 U.S.C.Section 371 filed from International Patent Application PCT/SE01/00559filed 16 Mar. 2001, which claims priority to United Kingdom patentapplication Serial. No. 0006527.6, filed 18 Mar. 2000. The contents ofthese applications are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

The present invention relates to a breath-actuated inhaler for deliveryof medicament by inhalation.

Inhalers are commonly used for delivery of a wide range of medicaments.A known type of inhaler holds a canister which is compressible todeliver a dose of medicament through a mouthpiece. It is known toprovide the inhaler with an actuation mechanism for compressing thecanister. The actuation mechanism may be breath-actuated to actuate thecanister in response to inhalation at the mouthpiece. Typically, abreath-actuated inhaler might include a loading mechanism for loading aresilient biassing element which is arranged when loaded to biascompression of the canister, and a triggering mechanism arranged to holdthe resilient biassing element against compression and to release theresilient loading element upon inhalation.

Known canisters comprise a body having a protruding valve stem and aninternal metering chamber which receives a dose of medicament from thebody where the medicament is stored under pressure. Compression of thevalve stem into the body causes the medicament in the metering chamberto be delivered out of the valve stem as a dose. The valve stem isbiassed outwardly to reset the canister after compression to deliver thenext dose of medicament. However, if the compression of the canister isreleased to allow reset of the valve stem too early, then a full dose isnot properly delivered. The present invention is intended to ensureproper delivery of a full dose.

BRIEF SUMMARY OF THE INVENTION

According to the present invention, there is provided an inhaler fordelivery of medicament from a canister which is compressible to delivera dose of medicament, the inhaler comprising:

a housing for holding a canister, the housing having a mouthpiece forinhalation of a dose of medicament delivered by the canister;

a breath-actuated actuation mechanism for compressing a canister held inthe housing in response to inhalation at the mouthpiece;

the actuation mechanism including a locking mechanism arranged to lockthe canister in a compressed state and being responsive to theinhalation at the mouthpiece to release the canister when the level ofinhalation at the mouthpiece falls below a predetermined threshold.

The locking mechanism ensures that reset of the canister does not occurimmediately but is delayed until the level of inhalation at themouthpiece falls below the predetermined threshold. Accordingly, a fulldose is properly delivered from the canister. Typically it is necessaryfor the user to take a deep breath to ensure proper inhalation of themedicament so the delay for reset of the canister is sufficiently long.

Preferably, the locking mechanism includes a vane responsive to airflowcreated by inhalation at the mouthpiece and arranged to release thelocking mechanism when the level of inhalation at the mouthpiece fallsbelow said predetermined threshold. A vane provides simple but reliabledetection of the level of inhalation falling below the predeterminedthreshold. Furthermore, the vane may also be arranged to trigger theactuation mechanism upon inhalation at the mouthpiece so that the vanehas a joint purpose. This simplifies the actuation mechanism of theinhaler and reduces the complexity of its airflow paths. Alternatively,an electronic sensor could be used to control the locking mechanismmaking it responsive to inhalation.

Preferably, the vane is disposed in a duct extending from themouthpiece. By providing the vane in a duct, it is possible to controlthe level of the predetermined threshold by appropriately designing theduct and the vane.

Desirably, the vane is a flap extending across the duct. This improvesthe reliability of operation, because it ensures that all the inhalationat the mouthpiece acts on the vane.

Desirably, the end of the duct opposite from the mouthpiece opens intothe interior of the housing. This ensures that the duct is protectedfrom the outside thereby assisting in preventing the vane from beinginterfered with and accidentally operated or else jammed, for example byinsertion of an object or finger. Preferably the vane is disposed at theend of the duct opposite from the mouthpiece. This increases thedistance of the vane from the mouthpiece, preventing interference withthe operation of the vane.

The present invention may be applied to an inhaler having an actuationmechanism which comprises a loading mechanism for loading a resilientbiassing element which is arranged, when loaded, to bias compression ofthe canister, and a triggering mechanism arranged to hold the resilientbiassing element against compression and triggerable to release theresilient biassing element.

Desirably, the loading mechanism drives a loading member coupled to theresilient loading element to load the resilient loading element, and thelocking mechanism is arranged to hold the loading element in a loadedstate, thereby locking the canister in its compressed state afterrelease of the triggering mechanism. Such a structure prevents thelocking element from interfering with the operation of the actuationmechanism to deliver a dose.

Preferably, the locking mechanism includes a moveable catch held in alocking position where the catch locks the canister in a compressedstate upon inhalation at the mouthpiece and released when the level ofinhalation at the mouthpiece falls below said predetermined threshold.

Desirably, the locking mechanism further comprises an intermediatemember coupled to the catch through a resilient biassing elementarranged to bias the catch towards the locking position, the loadingmechanism engaging the intermediate member upon inhalation at themouthpiece to load the resilient biassing member, thereby to hold thecatch in said locking position, and releasing the intermediate memberwhen the level of inhalation falls below said predetermined threshold tounload the resilient biassing element, thereby to release the catch. Theprovision of the resilient biassing element coupling the intermediatemember to the catch allows the catch to be forced open upon loading ofthe actuation mechanism.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

To allow better understanding, an inhaler which embodies the presentinvention will now be described by way of non-limitative example withreference to the accompanying drawings, in which:

FIG. 1 is a side view of the inhaler;

FIG. 2 is a cross-sectional view of the inhaler illustrating the housingand duct;

FIG. 3 is a side view of the duct;

FIG. 4 is a side view of the canister and duct assembled together;

FIG. 5 is an exploded view of the canister, collar and duct;

FIG. 6 is a cross-sectional view of the canister and dust assembledtogether;

FIG. 7 is a view from the side and rear of the actuation mechanism;

FIG. 8 is a view from the rear of the spindle;

FIG. 9 is a view from the side, rear and above showing the arrangementof the resilient loading element;

FIG. 10 is a schematic view of the cam surfaces formed on the spindle;

FIG. 11 is a view from the side and rear of the triggering mechanism;

FIG. 12 is a side view of the triggering mechanism;

FIG. 13 is a side view of the locking mechanism;

FIGS. 14A to 14F are graphs showing the angular positions of theelements of the actuation mechanism during its operation sequence; and

FIGS. 15 to 22 are views of the actuation mechanism in various statesduring its operation sequence with views from opposite sides beingsuffixed by the letters A, B respectively.

DETAILED DESCRIPTION OF THE INVENTION

As illustrated in FIG. 1, the inhaler has a housing 1 comprising anupper portion 19 and a lower portion 20. As illustrated in thecross-sectional view of FIG. 2, the upper housing portion 19 is a hollowshell which holds a canister 2 of medicament having a generallycylindrical body 3 held with its axis in a predetermined direction,vertical in FIG. 2. The upper housing portion 19 houses an actuationmechanism for actuating the canister 2 which will be described in moredetail below.

The interior of the upper housing portion 19 is open to the atmosphereby means of air inlets 51 formed in the upper wall 52 of the upperhousing portion 19. The location of the air inlets 51 minimisesocclusion by the users hand which will normally grip the sides of thehousing 1 and not cover the upper wall 52.

The canister 2 is compressible to deliver a dose of medicament. Inparticular the canister 2 has a valve stem 4 which is compressiblerelative to the body 3 to deliver a dose of medicament from the valvestem 4. The canister is of a known type including a metering chamberwhich captures a defined volume the medicament from the body 3 of thecanister 2. This volume of medicament is delivered as a metered dosefrom the valve stem 4 on compression of the valve stem 4 relative to thebody 3. The valve stem 4 is weakly biassed outwardly by an internalvalve spring (not shown) to reset the canister 2 after compression forrefilling the metering chamber.

The lower housing portion 20 is a hollow shell connected to the upperhousing portion 19 by a sliding joint (not shown) which allows the lowerportion 20 to be separated in the direction of the arrow in FIG. 1 bythe user gripping textured surfaces 21 formed on the upper and lowerhousing portions 19 and 20. A cap 22 is hinged to the lower housingportion 20 by a flexible joint 23 to cover and uncover a mouthpiece 5protruding from the lower housing portion 20.

As shown in FIG. 2, the lower housing portion 20 houses a duct 24 whichis integrally formed with the mouthpiece 5, as illustrated in isolationin FIG. 3.

The duct 24 is assembled with a canister 2 as shown in FIGS. 4 to 6. Theduct 24 receives a nozzle block 11 in an opening 25. The valve stem 4 ofthe canister is received in the nozzle block 11 which is arranged todirect a dose of medicament delivered from the valve stem 4 out of theinhaler through the mouthpiece 5. The duct 24 and nozzle block 11 areseparately formed. This allows each to be manufactured and subsequentlyassembled. This produces manufacturing and logistical savings because itfacilitates different nozzle block designs being incorporated with asingle duct design and vice versa.

A collar 26 is permanently connected to the canister 2. The collar 26includes an annular retaining ring 27 permanently fitted around a neckedportion 28 of the canister body 3. The retaining portion 27 preventsremoval of the collar 26 from the canister such that the collar 26 isremoved and replaced together with the canister 2. However, theretaining portion 27 and the canister 2 have a small degree of relativemovement along the axis of the canister 5 to allow compression of thecanister body 2 towards the valve stem 4.

The collar 26 further includes a front panel 29 integrally formed withthe retaining ring 27. When the canister 2 is inserted in the housing 1,the front panel 29 of the collar 26 closes an opening formed between theupper housing portion 19 and the lower portion 20 and therefore forms apart of the outer wall of the housing 1. Accordingly, the presence orabsence of the front panel 29 provides a visual indication to the userof whether or not a canister 2 has been inserted in the canister,because the collar 26 is permanently connected to the canister 2.

A pair of catch arms 30 integrally formed with the front panel 29 of thesides of the collar 26 catch the interior surface of the upper housingportion 19 to hold the collar 26 and the canister 2 in the upper housingportion 19.

The lower housing portion 20 has a stud 50 which locates the end of thenozzle block 11 as shown in FIG. 2 to hold the lower housing portion 20and the duct 24 in place relative to one another. However, the lowerhousing portion 20 is not retained on the duct 24, so may be removedfrom the upper housing portion 19 leaving the canister 2 inserted in theupper housing portion 19 and the duct 24 held on the canister 2 by thevalve stem 4 being inserted in the nozzle block 11. The duct 24 andnozzle block 11 may subsequently be slid off the valve stem 4 forcleaning or replacement. The canister 2 and collar 26 may be slid outfrom the upper housing portion 19 after depression of the catch arms 30.Subsequently a replacement canister 2 and collar 26 may be inserted.

Typically a new duct 24 and nozzle block 11 will be provided to the userwith each new canister 2 so that the duct 24 and mouthpiece 5 areregularly replaced to prevent damage or dirt building up over time. Theduct 24 has an opening 31 at its end opposite from the mouthpiece 5.

As shown in FIG. 2, the upper housing portion 19 holds a flap duct 32which extends from a flow inlet 33 to a flap 13 which forms part of thetriggering mechanism for the actuation mechanism as described in detailbelow. Therefore the duct 24 housed in the lower housing portion 19 andthe flap duct 32 together define a composite duct shaped to direct theinhalation flow from the mouthpiece 5 to the flap 13. The composite ductformed by the duct 24 and the flap duct 32 is shaped to control the flowto the flap 13 to provide appropriate flow characteristics for properoperation of the flap 13.

The inhaler is further provided with an actuation mechanism 6. To assistunderstanding, a general description of the overall structure andoperation of the actuation mechanism 6 will first be given.

An actuation force for compressing the canister 2 is stored in aresilient loading element in the form of a torsion spring 7. To load thetorsion spring 7, the actuation mechanism 6 includes a loading mechanismconsisting of a loading member in the form of a rotatable spindle 8 andtwo contact members in the form of buttons 9 which protrude from thehousing as shown in FIG. 1. Depression of the buttons 9 towards oneanother, relative to the housing 1, drives the loading member 8 to loadthe torsion spring 7 through a cam arrangement between the buttons 9 andspindle 8.

The torsion spring 7 biasses compression of the canister 2 by engaging acanister engagement member in the form of a lever 10 which depresses thebody 3 of the canister towards the stem 4 held in the nozzle block 11.

To allow storage of the actuation force in the torsion spring 7 afterloading, the actuation mechanism 6 includes a triggering mechanism. Thisincludes a locking lever 12 which holds the canister engagement lever 10against compression of the canister 2. To release the canisterengagement lever 10, the triggering mechanism further includes a vane inthe form of a flap 13 which in a rest state holds the locking lever 12in place. Inhalation at the mouthpiece 5 moves the flap 13 to releasethe locking member 12. This in turn releases the canister engagementlever 10 allowing the torsion spring 7 to drive compression of thecanister 2.

The actuation mechanism 6 further includes a locking mechanism whichlocks the spindle 8 after loading of the torsion spring 7, therebyholding the torsion spring 7 in its loaded state before triggering andlocking the canister in its compressed state after triggering.

The locking mechanism includes a catch 14 which, in a locking position,catches the spindle 8 and holds the torsion spring 7 in its loadedstate. The locking mechanism further includes an intermediate member 15.A resilient biassing element in the form of a spring 16 is providedbetween the catch 14 and the intermediate member 15 to bias the catch 14towards its locking position. The spring 16 allows deflection of thecatch 14 by the spindle 8 during loading of the torsion spring 7.

Prior to inhalation the intermediate member 15 is held in place by thecanister engagement lever 10. Upon inhalation at the mouthpiece 5, theflap 13 engages the intermediate member 15 to hold it in place. Aftercompression by the canister engagement lever 10, the canister 2 islocked in its compressed state by the catch 14 of the locking mechanismholding the spindle 8 in place.

When the level of inhalation at the mouthpiece falls below apredetermined threshold, the flap 13 releases the intermediate member 15to unload the biassing element 16 which in turn allows the catch 14 torelease the spindle 8. After release by the catch 14, the spindle 8,torsion spring 7 and canister engagement lever 10 move upwardly and thecanister resets.

Now there will be given a detailed description of the actuationmechanism 6, the entirety of which is illustrated in FIG. 7 and parts ofwhich are illustrated in FIGS. 8 to 13.

The loading mechanism is illustrated in FIG. 8 and consists of arotatable spindle 8 and two contact members in the forms of buttons 9 atboth ends. The spindle 8 is rotatably mounted in the upper housingportion 19 about an axis orthogonal to the axis of the cylindrical body3 of the canister 2. The spindle 8 has a pair of cam surfaces 8 adisposed on opposite sides of the rotational axis of the spindle 8. Thebuttons 9 are mounted in the housing to be movable in a movementdirection parallel to the rotational axis of the spindle 8. The buttons9 each have a pair of inwardly projecting cam followers 9 a which eachengage a respective cam surface 8 a of the spindle 8. The camarrangement of the cam surfaces 8 a and the cam followers 9 a betweenthe spindle 8 and the buttons 9 causes depression of the buttons 9 todrive rotation of the spindle 8.

As illustrated in FIG. 9, the torsion spring 7 which forms the resilientloading element is disposed with its coils 7 a encircling a centralcylindrical surface 8 b of the spindle 8. A catch arm 8 c protrudesradially from the spindle 8. A first leg 7 b of the torsion spring 7 isrestrained by the catch arm 8 c so that the movement of the spindle 8driven by the buttons 9 loads the torsion spring 7.

As illustrated schematically in FIG. 10, the cam surfaces 8 a have anon-linear shape which causes the gearing ratio of the amount of drivenmovement of the spindle 8 to the amount of movement of the buttons 9 tobe a non-linear function of the rotational position of the spindle 8.The major portion 8 b of each cam surface 8 a is shaped with increasingpitch to compensate for the increased reactive loading force applied bythe torsion spring 7 to the spindle 8 as the buttons 9 are depressed. Inparticular, they are shaped such that the necessary force applied to thebuttons is substantially constant so the user feels a linear resistance.As the torsion spring 7 has a linear spring constant, this is achievedby shaping the major portion 8 b of each cam surface 8 a such that thegearing ratio is inversely proportion to the rotational position of thespindle 8.

Optionally, the outermost portion of the cam surfaces 8 a which arecontacted by the cam followers 9 a during the initial portion of thedriven movement of the spindle may have a decreased pitch, for exampleas illustrated by the dotted lines 8 e. This is to reduce the gearingratio relative to the subsequent major portion 8 b. In this way the userinitially feels a low resistance to movement of the buttons 9. Thisimproves the feel perceived by the user and also assists the user inapplying force.

Another option is to provide the final portion of the cam surface 8 awith a detent, for example as illustrated by the dotted lines 8 d. Whenthe end of the cam followers 9 a reach the detent 8 d, the cam surface 8a of the spindle 8 no longer exerts a force urging the buttons outwardlyon the buttons 9. At this position the detent 8 dis urged by the torsionspring 7 against the side of the cam followers 9 a and therefore holdsthe buttons 9 in their innermost position. This prevents the buttons 9from loosely sliding back and forth after the torsion spring 7 has beenloaded.

As shown in FIG. 9, the torsion spring 7 engages a canister engagementlever 10 which is pivotally mounted to the interior of the housing aboutan axis 10 a. The canister engagement lever 10 is generally U-shapedwith two parallel sides 10 b connected by a cross piece 10 c. A bar 10 dextending between the two sides 10 b bears on the body 5 of the canister2. A mount 10 e formed on the cross-piece 10 c is engaged by the secondleg 7 c of the torsion spring 7, whereby loading of the torsion spring 7biasses the lever 10 to compress the canister 2. The canister engagementlever 10 is biassed upwardly by a reset spring (not shown), which may bearranged as a torsion spring on the axis 10 a, but this is weaker thanthe torsion spring 7.

The torsion spring 7, spindle 8 and canister engagement lever 10 are allrotatable about axis orthogonal to the cylindrical axis of the body 5 ofthe canister 2. This provides a simple and reliable loading mechanismparticularly because of the arrangement of the torsion spring 7 with itscoils 7 a encircling the spindle 8. Some or all of these elements couldalternatively be linearly movable in a plane parallel to the cylindricalaxis of the body 5 of the canister 2 to achieve a loading mechanismwhich is equally simple to construct. However rotatable elements arepreferred from the point of view of reliability in repeated use of theactuation mechanism 6.

On the other hand, the movement of the buttons in a direction orthogonalto the cylinder axis of the body 3 of the canister 2 assists the user inapplication of force to the loading mechanism. As typical for inhalers,the housing 1 extends in the direction of the cylindrical axis of thebody 3 of the canister 2, so may be easily held in the palm of a handwith the buttons 9 protruding from either side. Thus the buttons 9 areeasily depressed between a finger and thumb. Alternatively a singlebutton could be provided allowing loading in a similar manner by theuser pressing the button and the housing on the opposite side to thebutton. Either configuration also allows loading by laying the inhaleron a surface and applying force for example with the palm of a hand.This facilitates loading by a user with limited finger control ormovement, for example a chronic arthritis sufferer.

The actuation member mechanism 6 includes a triggering mechanism asillustrated in FIGS. 11 and 12 which allows storage of the actuationforce in the torsion spring 7 after loading.

The triggering mechanism includes a locking lever 12 which is pivotablymounted on an axle 17 extending across the interior of the housing 1.The locking lever 12 has a notch 12 a adjacent the axle 17. In a resetstate shown in FIG. 12, the notch 12 a holds a protrusion 10 fprotruding from the cross-piece 10 c of the canister engagement lever10, thereby holding the lever 10 against compression of the canister 2.The locking lever 12 is weakly biassed towards the position shown inFIGS. 11 and 12 by a reset spring 34 arranged as a torsion spring on theaxle 17.

The triggering mechanism further includes a vane in the form of a flap13 which is rotatably mounted on an axle 18 extending across theinterior of the housing 1. The flap 13 biassed by a reset spring (notshown), which may be arranged as a torsion spring on the axle 18,towards the position shown in FIG. 12. The flap 13 has a locking leverengagement surface 13 a which protrudes from a block 13 b positionedabove the axle 18. In the position shown in FIG. 12, the engagementsurface 13 aengages a contact surface 12 b formed on the end of thelocking lever 12 distal from the axle 17 to hold the locking lever 12 inplace holding the canister engagement lever 10.

The flap 13 is disposed in the composite duct formed by the duct 24 andthe flap duct 32 extending from the mouthpiece 5 with a flap portion 13c extending across the composite duct at the opposite end from themouthpiece 5, where the duct opens into the interior of the housing 1.Therefore, the flap 13 is responsive to inhalation at the mouthpiece 5.

Inhalation of the mouthpiece draws the flap portion 13 c into the flapduct 32 (clockwise in FIG. 2 and anticlockwise in FIG. 12). Suchrotation of the flap 13 allows the locking lever engagement surface 13 ato move out of contact with the contact surface 12 b of the lockinglever 12.

The upper housing portion 19 also mounts a button 35 disposed adjacentthe flap 13 above the axle 18 so that depression of the button 35rotates the flap 13 in the same direction as inhalation at themouthpiece 5. Therefore, the button 35 allows the actuation mechanism 6to be manually released without inhalation at the mouthpiece 5, forexample to allow actuation of the canister 2 for testing.

When the canister engagement lever 10 is loaded by the torsion spring 7,release of the locking lever 12 by the flap 13 allows the canisterengagement lever 10 to be driven to compress the canister 2. Theprotrusion 10 f deflects the locking lever 12 (anticlockwise in FIG. 12)as the canister engagement lever 10 passes.

As illustrated in FIG. 13, the actuation mechanism 6 further includes alocking mechanism for locking the spindle 8 after loading of the torsionspring 7. The locking mechanism comprises a catch 14 and an intermediatemember 15 which are both pivotally mounted on the axle 17, adjacent thelocking lever 12. Before compression of the canister 2, the intermediatemember 15 is held in the position illustrated in FIG. 13 by thecross-piece 10 c of the canister engagement lever 10 contacting a firstcontact surface 15 a adjacent the axle 17. A resilient biassing elementin the form of a torsion spring 16 is connected between the catch 14 andthe intermediate member 15 and loaded to bias the catch 14 towards itslocking position shown in FIG. 13.

The catch 14 has a notch 14a adjacent the axle 17 for engaging the arm 8c of the spindle 8 after rotation to the position illustrated in FIG. 13where the torsion spring 7 is loaded. In this position, the loadingprovided by the spring 16 prevents release of the spindle 8 and therebyholds the torsion spring 7 in its loaded state. Before loading, the arm8 c of the spindle 8 is positioned above the end 14 b of the catch 14distal from the axle 17. When the spindle 8 is driven downwards bydepression of the buttons 9, the arm 8 c of the spindle engages the end14 b of the catch 14 and deflects the catch 14 by compressing the spring16 to allow passage of the arm 8 c of the spindle 8.

The flap 13 further includes a stud 13 d protruding from the block 13 bon the opposite side of the axle 18 from the locking lever engagementsurface 13 a. Upon inhalation at the mouthpiece 5, the flap 13 moves tothe position illustrated in FIG. 13 where the stud 13 d engages a secondcontact surface 15 b of the intermediate member 15 distal from the axle17. Prior to this point, the stud 13 d does not contact the secondcontact surface 15 b but the intermediate member 15 has been held inplace by the canister engagement lever 10. Movement of the flap 13triggers the triggering mechanism to release the canister engagementmember 10 which moves downwards out of contact with the intermediatemember 15. However, the stud 113 d catches the contact surface 15 b andso continues to hold the intermediate member 15 with the spring 16loaded. Accordingly, the catch 14 remains in its locking positionlocking the spindle 8 by engagement of the arm 8 c of the spindle 8 inthe notch 14 a of the catch 14.

Subsequently, when the level of inhalation of the mouthpiece falls belowa predetermined threshold, the flap moves out of contact with theintermediate member 15 (clockwise in FIG. 13). The level of thepredetermined threshold at which the flap 13 releases the intermediatemember 15 is controlled by the shape of the second contact surface 15 bof the intermediate member 15.

After release by the flap 13, the intermediate member 15 is driven byspring 16 which unloads (clockwise in FIG. 13). Such unloading of thespring 16 reduces the force by which the catch 14 is biassed towards itslocking position. Accordingly, the force of the torsion spring 7 actingon the canister engagement lever 10 is sufficient to force the catch arm8 c of the spindle 8 out of the notch 14 a. Accordingly, the spindle 8,the torsion spring 7 and canister engagement lever 10 are able to moveupwardly biassed by the reset spring acting on the canister engagementlever 10, thereby allowing the canister to reset.

The sequence of operation of the actuation mechanism 6 will now bedescribed with reference to FIGS. 14 to 22. FIGS. 14A to 14F are graphsshowing the 10 angular positions of the various elements of theactuation mechanism 6. In particular, FIG. 14A illustrates the angularposition of the flap 13; FIG. 14B illustrates the angular position ofthe locking lever 12; FIG. 14C illustrates the angular position of thecanister engagement lever 10; FIG. 14D illustrates the angular positionof the intermediate member 15; FIG. 14E illustrates the angular positionof the catch 14; and FIG. 14F illustrates the angular position of thespindle 8. Various states and positions of the actuation mechanism 6 arelabelled by the letters A to R in FIG. 14 and FIGS. 15 to 22 illustratethe actuation mechanism 6 in some of these states with the views fromopposite sides being suffixed by the letters A and B, respectively.

The sequence commences in state A as shown in FIG. 15 in which thetorsion spring 7 has been loaded by depression of the buttons 9 and thespindle 8 is locked by the catch 14. In state A, the canister engagementlever is 10 held by the locking lever 12. The inhaler may be stored withthe actuation mechanism 6 in state A.

At position B, the user starts to inhale. The flap 13, being responsiveto such inhalation, starts to move. The shape of the contact surface 12b allows the locking lever 12 to start moving slowly. The actuationmechanism 6 is now in state C illustrated in FIG. 16.

At position D, the locking lever engagement surface 13 a of the flap 13releases the contact surface 12 b of the locking lever 12. Accordingly,the canister engagement member 10 under the loading of the torsionspring 7 starts to rotate downwards deflecting the locking lever 12against its reset spring as the projection 10 f moves out of the notch12 a The actuation mechanism is now in state E illustrated in FIG. 17.

At position F, the canister engagement lever 10 moves out of contactwith the first contact surface 15 a at the intermediate member 15 whichtherefore starts to move under the biassing of spring 16. However, theintermediate member 15 only moves a short way because at position G itis caught by the flap 13, in particular by the bar 13 d of the flap 13contacting the second contact surface 15 b. This contact stops themovement of the flap 13 and the intermediate member 15.

The movement of the canister engagement lever 10 compresses the body 3of the canister 2 relative to the stem 4 held in the nozzle block 11,thereby causing the canister 2 to deliver a dose of medicament. Thenozzle block 11 directs the dose of medicament out of the mouthpiece atwhich the user is inhaling. The actuation mechanism 6 is now in state Hillustrated in FIG. 18.

When the level of inhalation starts to fall, at position I the flap 13under the biassing of its reset spring starts to move back closing theduct This movement of the flap 13 causes the intermediate member 15 tomove slightly due to the shape of the second contact surface 15 b.

When the level of inhalation falls below the predetermined threshold, atposition J the bar 13 d of the flap 13 moves out of contact with thesecond contact surface 15 b. This releases the intermediate member 15.Under the action of the spring 16, the intermediate member 15 moves tounload the spring 16. The actuation mechanism 6 is now in state Killustrated in FIG. 19.

At position L the load on the catch 14 from the spring 16 reduces to theextent that the catch 15 can no longer hold the spindle 8. The force ofthe torsion spring 7 forces the arm 8 c of the spindle 8 upwards and outof engagement with the notch 14 a of the catch 14. This forces the catch14 backwards. The actuation mechanism 6 is now in state M illustrated inFIG. 20.

At position N, the torsion spring 7 reaches its neutral, unloadedposition, so there is no load between the canister engagement lever 10and the spindle 8. Thereafter the canister engagement lever 10 and thetorsion spring 8 are moved under the action of the reset spring biassingthe canister engagement lever 10.

At position O, the canister engagement lever 10 contacts the firstcontact surface 15 a of the intermediate member 15 and forces itbackwards. The actuation mechanism is now in state P illustrated in FIG.21. This loads the spring 16 and pushes the catch 14 towards its lockingposition until the catch 14 contacts the arm 8 c of the spindle 8 whichhas now passed out of the notch 14 a.

At position Q, the projection 10 f of the canister engagement lever 10moves into the notch 12 a of the locking lever 12 which snaps back intoits locking position under the action of its reset spring. The actuationmechanism 6 is now in state R in FIG. 22. In state R, the canister isreset and ready to be compressed again for delivery of the next dose,but the actuation mechanism 6 is relaxed with the torsion spring 7unloaded. The rotation of the spindle 8 has forced the buttons 9outwards to the position illustrated in FIG. 22. The actuation mechanism6 is ready to be loaded once again by compression of the buttons 9. Theuser is instructed to do this immediately after inhalation, so that thecanister may be stored in a state ready to be used simply by inhaling atthe mouthpiece 5.

When the user depresses the buttons 9 at position S, this drives thespindle 8 downwards . The arm 8 c of the spindle 8 deflects the catch 14slightly against the loaded spring 16 until the arm 8 c moves into thenotch 14 a. This allows the spring 16 to snap the catch 14 into itslocking position.

What is claimed is:
 1. An inhaler for delivery of medicament from acanister which is compressible to deliver a dose of medicament, theinhaler comprising: a housing for holding a canister, the housing havinga mouthpiece for inhalation of a dose of medicament delivered by thecanister; a breath-actuated actuation mechanism for compressing acanister held in the housing in response to inhalation at themouthpiece; the actuation mechanism including a locking mechanismarranged to lock the canister in a compressed state and being responsiveto the inhalation at the mouthpiece to reset the canister to anuncompressed state when the level of inhalation at the mouthpiece fallsbelow a predetermined threshold.
 2. An inhaler according to claim 1,wherein the locking mechanism includes a vane responsive to airflowcreated by inhalation at the mouthpiece and arranged to release thelocking mechanism when the level of inhalation at the mouthpiece fallsbelow said predetermined threshold.
 3. An inhaler according to claim 2,wherein the vane is disposed in a duct extending from the mouthpiece. 4.An inhaler according to 3, wherein the vane is a flap extending acrossthe duct.
 5. An inhaler according to claim 2, wherein the end of theduct opposite from the mouthpiece opens into the interior of thehousing.
 6. An inhaler according to claim 2, wherein the vane isdisposed at the end of the duct opposite from the mouthpiece.
 7. Aninhaler according to claim 2, wherein the vane is arranged to triggerthe actuation mechanism upon inhalation at the mouthpiece.
 8. An inhaleraccording to claim 1, wherein the actuation mechanism includes: aloading mechanism for loading a resilient biassing element which isarranged, when loaded, to bias compression of the canister, and atriggering mechanism arranged to hold the resilient biassing elementagainst compression and triggerable to release the resilient biassingelement.
 9. An inhaler according to claim 8, wherein the lockingmechanism includes a vane responsive to airflow created by inhalation atthe mouthpiece and arranged to release the locking mechanism when thelevel of inhalation at the mouthpiece falls below said predeterminedthreshold, wherein the vane is arranged to trigger the triggeringmechanism upon inhalation at the mouthpiece.
 10. An inhaler according toclaim 8, wherein the loading mechanism drives a loading member coupledto the resilient loading element to load the resilient loading element,and the locking mechanism is arranged to hold the loading element in aloaded state, thereby locking the canister in its compressed state afterrelease of the triggering mechanism.
 11. An inhaler according to claim10, wherein the locking mechanism further comprises an intermediatemember coupled to the catch through a resilient biassing elementarranged to bias the catch towards the locking position, the loadingmechanism engaging the intermediate member upon inhalation at themouthpiece to load the resilient biassing member, thereby to hold thecatch in said locking position, and releasing the intermediate memberwhen the level of inhalation falls below said predetermined threshold tounload the resilient biassing element, thereby to release the catch. 12.An inhaler according to claim 11, wherein the locking mechanism includesa vane responsive to airflow created by inhalation at the mouthpiece andarranged to release the locking mechanism when the level of inhalationat the mouthpiece falls below said predetermined threshold, wherein theintermediate member is engaged and released by the vane.
 13. An inhaleraccording to claim 12, wherein the intermediate member and the vane havecontact surfaces and the predetermined threshold is controlled by theshape of the contact surfaces of the intermediate member and the vane.14. An inhaler according to claim 1, wherein the locking mechanismincludes a moveable catch held in a locking position where the catchlocks the canister in a compressed state upon inhalation at themouthpiece and releases the canister when the level of inhalation at themouthpiece falls below said predetermined threshold.
 15. An inhaleraccording to claim 14, wherein the catch is rotatable.
 16. An inhaleraccording to claim 14, wherein the intermediate member is rotatable. 17.An inhaler according to claim 14, wherein the catch and the intermediatemember are rotatable about a common axis.